Oxidation kinetics of nickel nanoparticles

The oxidation kinetics of nickel particles with an approximate median size of 15 nm was determined by thermogravimetry. The particles had a thin initi al oxide shell amounting to 36 wt % of the sample. The kinetics was studied in pure oxygen in the temperature range 135-235 degreesC, giving power law behavior of each isotherm with an exponent between 0.48 and 0.58. By use o f a master plot technique an apparent activation energy of 1.34 eV was dete rmined. The power law exponent is considerably lower than the one expected for diffusion limited oxidation of a spherical particle with an initial oxi de shell. The deviations from parabolic kinetics are discussed in terms of nonlinear diffusion, grain growth, and particle agglomeration. (C) 2001 Ame rican Institute of Physics.